Optical networks include various optical switches or nodes coupled through a network of optical fiber links. Optical network failures or faults may be caused by any number of events or reasons, including damaged or severed optical fibers, or equipment failure. Because optical fibers may be installed virtually anywhere, including underground, above ground or underwater, they are subject to damage through a variety of ways and phenomena. Optical fibers and optical equipment may be damaged or severed, for example, by lightning, fire, natural disasters, traffic accidents, digging, construction accidents, and the like.
Because optical fibers carry far greater amounts of information than copper wires used to transmit electrical telecommunications signals, the loss of an optical fiber can cause far more user disruptions when compared with the loss of a copper wire. For example, the loss of a single optical link, such as an optical link carrying a Wavelength Division Multiplexed (“WDM”) signal, may result in the loss of hundreds of thousands of phone calls and computer data transmissions. Additionally, dozens of fibers may be routed within a single cable or conduit, substantially increasing the risk of loss associated with a damaged cable or conduit.
To reduce the negative effects of optical network failures, optical network topologies are provided in arrangements and configurations, such as mesh or ring topologies, so that telecommunications traffic may traverse the optical network using multiple optical links. This allows such optical networks to be reconfigured to route around network failure point. An optical network may include both working links or paths and spare links or paths that may be used to assist with optical network restoration. Due to the large amount of data or bandwidth an optical network carries, the amount of time it takes to identify the location of an optical network failure, and the time it takes then to reconfigure the optical network, may result in significant amounts of telecommunications traffic being lost. In particular, the reconfiguration of an optical network may result in the loss of other telecommunications traffic if not done efficiently or optimally.
Known restoration techniques and methodologies are generally designed to restore telecommunications networks operating in the electrical domain as opposed to the optical domain, which presents additional challenges. Unfortunately, switching and restoration in the electrical domain, while fast, results in a significant waste of fiber resources, in that entire optical links are removed from service, even when only a small portion of the fiber is in need of maintenance.
Another technique involves the use of a central control and database to model the network, monitor network operations, and communicate instructions to each node or optical switch in the network in response to a failure. Unfortunately, as fiber counts and network bandwidth requirements increase, the ability to efficiently switch signals in the optical domain is significantly reduced.